The present invention pertains to high-temperature resistant resins and, more particularly, to dicyanophenoxy compounds and the cyano-addition resins prepared therefrom.
It is known that certain bisorthodinitriles polymerize to form strong, high-temperature-resistant thermosetting resins. Such suitable bisorthodinitriles are disclosed for example, in U.S. Pat. Nos. 4,056,560, 4,057,569, 4,067,086 and 3,993,631 to James R. Griffith and Jacque O'Rear. U.S. Pat. Ser. Nos. 051,568 (now U.S. Pat. No. 4,226,801), 043,188 (now U.S. Pat. No. 4,223,123), and 075,631 (now U.S. Pat. No. 4,234,712) are further examples of polyphthalcyanines having improved properties.
Several resins, particularly epoxies and polyimides, are finding increasing use in industry. These resins are becoming increasingly used as substitutes for metals when reinforced by various fibers and molded into structural materials. These composites have superior mechanical properties as well as being lighter and more economical. One particular advantage of such materials is the amount of fuel saved by moving structures manufactured from these lightweight materials.
These resins have several disadvantages, however. Conventional epoxy-based composites are limited to a maximum service temperature of 120.degree. C.; other problems associated with these composites include their brittleness, water absorptivity, and engineering reliability. While aromatic polyimides have a greater thermal stability than epoxy resins, their use has not been as extensive as epoxy resins because of their insolubility in organic solvents needed in synthesis, their poor reproducibility on account of the release of water which often splits polymeric chains, trapped solvents in the final resin, and excessive stiffness.
Recently, a new class of resins has been obtained by polymerizing certain phthalonitrile-terminated diamides, often referred to as amide-bridged bisorthodinitriles. These resins have a comparable structural strength to those currently available, in addition to possessing several beneficial properties which are not found in epoxies and polyimides.
Their maximum service temperature stability in an oxygen-containing atmosphere is well over 100.degree. C. greater than that for epoxies. Water absorptivity as measured by the water-soak method is also much lower than that for epoxies. Several of these resins, depending on the bridging chain, have a much greater elastic modulus than epoxy and polyimide resins. These resins have many other advantages over polyimides, due to an absence of solvents in their preparation, lower water absorptivity, as well as not being thermoplastic with a low glass-transition temperature.
Many applications require a structural composite to have an elastic modulus high enough to withstand numerous mechanical stresses and strains over a long period of time. One application is the underbody of jet aircraft exposed to the back blast of jet engines, especially the V/STOL (vertical/short take-off and landing) aircraft. Structural components of helicoptor and automobile frames are also exposed to severe mechanical demands.